Neurons are highly polarized cells that are specialized for information processing in the nervous system and depend upon microtubule (MT)- based transport systems for their assembly, maintenance and function. For example, chemosensory neurons in the nematode, Caenorhabditis elegans, are bipolar cells that use ciliated dendrites to detect chemicals in the environment (e.g. chemoattractants released by their bacterial food) and that transmit signals from their axons to coordinate the appropriate motile response (e.g. movement towards the source of the chemoattractant). We hypothesize that the formation and function of dendrites and sensory cilia on these chemosensory neurons depend upon MT-based intradendritic and intraciliary transport driven by two heteromeric kinesins, heterotrimeric kinesin-ll and dimeric Osm-3, whereas neurotransmission depends upon axonal transport driven, in part, by the monomeric kinesin, Unc-104. To test this hypothesis, the specific aims are: 1. To use EM and an in vivo transport assay to characterize the basic transport apparatus (i.e. motors, MT tracks and transport rafts/vesicles) operating in chemosensory neurons. 2. To dissect the functional relationships between the kinesin-Il and Osm-3 transport pathways in the formation and function of dendrites and sensory cilia. 3. To dissect the roles of Unc-104 in the binding and axonal transport of synaptic vesicles. 4. To study the relationship between intraciliary transport and chemosensory behavior of the adult C. elegans. Collectively, these studies will improve our understanding of the role of MT-based transport in the formation and function of neurons and in the control of the behavior of a primitive metazoan.